Announcements

Call/email a semi-pro. There are many free sources of help on the web and the phone.
USA: National Suicide Prevention Lifeline at 1-800-273-8255 or 1-800-SUICIDE - 24 hours a day
Australia: Lifeline at 13 11 14 - 24 hours a day
New Zealand: Lifeline at 0800 543 354 - 24 hours a day
Ireland: Samaritans at 1850 60 90 90 - 24 hours a day
UK: Samaritans at 08457 90 90 90 - 24 hours a day
Canada: Try a number from here
Canada/Youth (under 20): Kids' Help Phone at 1-800-668-6868 - 24 hours a day (anonymous and confidential - can't trace calls)
Canada and USA / Youth: Covenant House Nineline at 1-800-999-9999 (2 pm til midnight)
Trans* Folks: (877) 565 8860 - by and for trans* folks in North America - translifeline.org
If you don't want to chat on the phone, you can chat with a trained volunteer online here: https://www.imalive.org
Websites and other info:
You can call The Samaritans if you are in Ireland (1850 60 90 90) or the UK (08457 90 90 90), . They provide "confidential non-judgemental emotional support 24 hours a day". You can contact them by email, phone, or letter, or talk to someone face to face at one of their branches.
If you are in Australia, you can contact Lifeline at 13 11 14. They are open 24 hours a day. If you would prefer, you can also try out their online crisis chat which is open from 8 pm - 4am AEST. People from New Zealand can also call Lifeline - see number above. NZ folks can also see this website for a list of helplines: http://www.mhc.govt.nz/urgent-help
If you are in the US, you can call the National Suicide Prevention Lifeline at 1-800-273-8255 24 hours a day.
If you are in Canada, you can try this list of regional crisis lines (mainly in Ontario).
If you are in Canada and under 20, you can call Kids' Help Phone at 1-800-668-6868 (it's confidential and they can't trace your call).
If you are in Canada and you require support in French, Suicide Action Montreal operates a bilingual line: (514) 723-4000
If none of these are in your area, you can try searching "suicide or crisis helpline in [insert your location here]."
If you STILL can't find anything and you need to talk to someone now, try calling one of the above lines, even if it isn't in your area.
Here are some websites that provide support and information about suicide and suicide prevention. They may also contain lists of helplines that are not listed above:
http://www.metanoia.org/suicide/
http://www.suicide.org/
http://suicide.com/
http://suicidal.com/